Abstract
BackgroundTo investigate the occupational risk of tuberculosis (TB) infection in a low-incidence setting, data from a prospective study of patients with culture-confirmed TB conducted in Hamburg, Germany, from 1997 to 2002 were evaluated.MethodsM. tuberculosis isolates were genotyped by IS6110 RFLP analysis. Results of contact tracing and additional patient interviews were used for further epidemiological analyses.ResultsOut of 848 cases included in the cluster analysis, 286 (33.7%) were classified into 76 clusters comprising 2 to 39 patients. In total, two patients in the non-cluster and eight patients in the cluster group were health-care workers. Logistic regression analysis confirmed work in the health-care sector as the strongest predictor for clustering (OR 17.9). However, only two of the eight transmission links among the eight clusters involving health-care workers had been detected previously. Overall, conventional contact tracing performed before genotyping had identified only 26 (25.2%) of the 103 contact persons with the disease among the clustered cases whose transmission links were epidemiologically verified.ConclusionRecent transmission was found to be strongly associated with health-care work in a setting with low incidence of TB. Conventional contact tracing alone was shown to be insufficient to discover recent transmission chains. The data presented also indicate the need for establishing improved TB control strategies in health-care settings.
Highlights
To investigate the occupational risk of tuberculosis (TB) infection in a low-incidence setting, data from a prospective study of patients with culture-confirmed TB conducted in Hamburg, Germany, from 1997 to 2002 were evaluated
Mycobacterium tuberculosis strains with DNA fingerprint patterns that are identical in respect of the insertion sequence
IS6110 indicate possible transmission chains, and on the basis of this it has been concluded [6] that recently transmitted infections with rapid progress to active TB seem generally to play an important part in the spread of TB
Summary
To investigate the occupational risk of tuberculosis (TB) infection in a low-incidence setting, data from a prospective study of patients with culture-confirmed TB conducted in Hamburg, Germany, from 1997 to 2002 were evaluated. Several population-based studies – e.g. in Europe or the USA [1,2,3,4,5] – have, by applying both classical epidemiological and molecular strain-typing techniques, revealed a high frequency of transmission of tuberculosis (TB), even in countries with a low TB incidence. Only a few studies have been performed that have applied modern molecular DNA-fingerprint techniques capable of tracing directly routes of transmission attributable to occupational exposure, e.g. among healthcare workers [5,7,8,9]. In 2001, as in previous years, Hamburg had a TB incidence rate higher than in any of the other fifteen German federal states
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